JP5884172B2 - COMMUNICATION DEVICE, COMMUNICATION METHOD, AND PROGRAM - Google Patents

Description

  The present invention relates to a communication device that performs communication using a vacant frequency band.

  Conventionally, in the ISM (Industry-Science-Medical) band or the like, a concept of dynamic spectrum access (DSA) that accumulates fragmented free frequency bands and uses it as one radio channel has been proposed (for example, Non-patent document 1). As a spectrum control method suitable for the DSA, a spectrum division single carrier modulation method has been proposed in which a spectrum of single carrier modulation is divided into a plurality of bands by a bandpass filter, and each frequency is converted and transmitted (for example, Patent Document 1, Non-Patent Document 2).

  Conventionally, when a data frame cannot be properly received on the receiving side, such as an automatic repeat request (ARQ: Automatic Repeat-reQuest), the data frame is automatically retransmitted. .

JP 2010-232857 A

Taro Maruma, Hitoshi Yano, Seiji Tsukamoto, Masazumi Ueha, “Proposal of Dynamic Spectrum Access System for Highly Efficient Frequency Sharing in ISM Band”, IEICE Technical Report, vol. 108, no. 446, SR2008-97, p. 53-57, March 2009 Yasuo Suzuki, Makoto Taro Maru, Hitoshi Yano, Masazumi Kamiha, “Basic performance of spectrum division single carrier transmission system with band limitation for DSA”, IEICE Tech. 109, no. 164, RCS 2009-81, p. 19-23, August 2009

  With the above automatic retransmission request, highly reliable data communication can be performed. However, since communication using a free frequency band detects a free frequency band by carrier sense (spectrum sensing) and performs communication using that frequency band, it is not guaranteed to ensure a short-term / periodic transmission opportunity. . Therefore, it is not always possible to reliably retransmit according to the timeout. In addition, a delay occurs due to the retransmission sequence. Therefore, there is a problem that the conventional automatic retransmission request is not suitable as a method for improving the quality in communication performed using an empty frequency band.

  The present invention has been made to solve the above-described problem, and an object of the present invention is to provide a communication device and the like that can reduce a bit error rate in communication performed using an empty frequency band.

In order to achieve the above object, a communication device according to the present invention is a communication device that performs communication using a vacant frequency band, and a communication unit that communicates communication data and a vacant frequency that is a frequency band that is not used for communication. A specifying unit for specifying a band; a determination unit for determining a repetition number indicating the number of data to be repeated included in communication data according to an empty frequency band specified by the specifying unit; and a symbol after modulation of the data to be repeated A control unit that causes the communication unit to transmit communication data including the number of repetitions determined by the determining unit using the vacant frequency band specified by the specifying unit.
With such a configuration, when communication data repeatedly including a symbol sequence can be transmitted, the repetition target data can be made redundant by performing the repetition. As a result, the bit error rate can be reduced and the communication quality can be improved. In addition, since the number of repetitions is determined according to the vacant frequency band, for example, it is possible to perform redundancy within a range that does not affect other communications such as interference.

In the communication device according to the present invention, the determining unit may determine the maximum number of repetitions that can repeat the data to be repeated in the vacant frequency band specified by the specifying unit.
With such a configuration, maximum redundancy according to the free frequency band can be performed, and communication quality can be improved.

In the communication device according to the present invention, the determination unit may determine the number of repetitions equal to or less than a predetermined upper limit value.
With such a configuration, by setting an appropriate upper limit value, it becomes possible to perform communication in consideration of communication opportunities by other devices.

In the communication device according to the present invention, the communication unit may also transmit repetitive information that is information that can identify a repeated symbol sequence included in the communication data.
With such a configuration, it is possible to repeatedly transmit information to a communication destination device. As a result, for example, the communication destination device can specify the repeated symbol series by using the repetition information, and can reduce the bit error rate by synthesizing the specified symbol series. .

  In addition, the communication method according to the present invention is a communication method for performing communication using an empty frequency band, and includes a specifying step for specifying an empty frequency band that is a frequency band not used for communication, and an empty space specified in the specifying step. A determination step for determining the number of repetitions indicating the number of data to be repeated included in the communication data according to the frequency band, and communication data including the number of repetitions determined in the determination step for the symbol sequence after modulation of the data to be repeated And a control step of transmitting using the vacant frequency band specified in the specifying step.

  According to the communication apparatus or the like according to the present invention, the bit error rate can be reduced by transmitting communication data that repeatedly includes data to be repeated according to an available frequency band.

The block diagram which shows the structure of the communication apparatus by Embodiment 1 of this invention. The block diagram which shows the structure of the communication part by the embodiment The flowchart which shows operation | movement of the communication apparatus by the embodiment The figure which shows an example of the structure of the data in the embodiment The figure which shows an example of a response | compatibility with the modulation system etc. in the same embodiment, and the number of transmittable bytes Schematic diagram showing an example of the appearance of a computer system in the present embodiment The figure which shows an example of a structure of the computer system in this Embodiment

  Hereinafter, a communication device according to the present invention will be described using embodiments. In the following embodiments, components and steps denoted by the same reference numerals are the same or equivalent, and repetitive description may be omitted.

(Embodiment 1)
A communication apparatus according to Embodiment 1 of the present invention will be described with reference to the drawings. The communication apparatus according to the present embodiment transmits communication data repeatedly including data to be repeated according to the situation of the vacant frequency band.

  FIG. 1 is a block diagram showing a configuration of a communication apparatus 1 according to the present embodiment. The communication device 1 according to the present embodiment performs communication using a vacant frequency band, and includes a communication unit 11, a specifying unit 12, a determination unit 13, and a control unit 14. In the present embodiment, a case where the communication device 1 is a mobile station (MS: Mobile Station) and an access point (AP: Access Point) that is a communication destination device of the communication device 1 is mainly described. Needless to say, this is not necessary. The communication device 1 may be an AP.

  The communication unit 11 communicates communication data. The communication of the communication data may be communication divided into a plurality of sub-spectrums corresponding to a plurality of frequency bands by, for example, a spectrum division single carrier modulation method, or may not be. The communication other than the spectrum division single carrier modulation method may be, for example, communication of a single carrier modulation method that does not perform spectrum division, may be communication of a multicarrier modulation method that does not perform spectrum division, or Multi-carrier modulation communication that performs spectrum division may be used. In any communication, the communication unit 11 performs communication data communication using one or a plurality of frequency bands. The one or more frequency bands are selected from unused frequency bands specified by the specifying unit 12 and are specified by the control unit 14 as will be described later. The communication by the communication unit 11 may be transmission or transmission / reception. In the present embodiment, the case where the communication unit 11 performs transmission / reception by the spectrum division single carrier modulation method will be mainly described. In addition, for example, when carrier sense is performed during communication and communication is performed using an empty frequency band at that time, the frequency band or bands used in the communication are appropriately determined during communication. It can be switched.

  The communication unit 11 may also transmit repetitive information that is information that can identify a repeated symbol sequence included in the communication data. This is because the destination apparatus can identify the symbol series based on the repetition information and synthesize a plurality of symbol series. The repetition information may be information that can specify the amount of repeated data (for example, the number of bits, the number of bytes, etc.), for example. Note that the information that can identify the amount of repeated data may be, for example, the amount of repeated data itself, or may be information that allows the amount of repeated data to be known. In the latter case, for example, when the data to be repeated includes predetermined data (for example, information for error detection and trellis bits), the amount of data excluding the predetermined data is used. There may be. This is because by using the amount of data, the amount of repeated data itself can be known as a result. Further, the repetition information may or may not include the number of repetitions. In addition, when the data to be transmitted includes both the data to be repeated and the data not to be repeated, the repetition information may include information that can specify the amount of the data that is not the repetition target. Alternatively, it may not be included. Further, the communication unit 11 may transmit the repetitive information via a control channel used for communication of control data or the like, or may transmit the repetitive information together with data to be transmitted via a data channel. In the latter case, for example, in the data to be transmitted, the data to be repeated is the object to be repeated, and the data including the repetition information (for example, the header of the packet including the data to be repeated in the payload) is the object to be repeated. It may not be necessary. This is because, at the time of reception, it is necessary to be able to acquire (demodulate) repeated information before performing synthesis according to repetition.

  In addition, when the communication unit 11 receives communication data including repetition target data corresponding to the number of repetitions, the communication unit 11 also receives repetition information that can identify a repeated symbol series included in the communication data. May be. The repetition information may be information transmitted from a communication partner device, for example. Moreover, the communication part 11 may receive information repeatedly via the control channel used by communication, such as control data, for example, or may transmit via a data channel with the data of transmission object. In the latter case, as described above, the data including the repetition information is not the object of repetition, and the repetition information is obtained by demodulating only the data first, and the repetition information is used to repeat the data. The symbol series corresponding to the target data may be combined and the combined symbol series may be demodulated.

  The communication unit 11 may or may not perform channel access based on CSMA / CA (Carrier Sense Multiple Access Collision Aidance) in units of a predetermined time frame (for example, 5 ms). Good. Further, the communication unit 11 may implement multiple access in a cell by TDMA / TDD (Time Division Multiple Access / Time Division Multiplex) in units of slots obtained by dividing a time frame in the channel access. Or it may not be so.

  FIG. 2 is a block diagram showing a detailed configuration of the transmission system 11a (FIG. 2A) and the reception system 11b (FIG. 2B) in the communication unit 11. As shown in FIG. The transmission system 11a transmits the communication data by dividing it into a plurality of sub-spectrums corresponding to a plurality of frequency bands by a spectrum division single carrier modulation method. The receiving system 11b receives the communication data transmitted by being divided into a plurality of sub-spectrums corresponding to a plurality of frequency bands by a spectrum division single carrier modulation method.

  2A, the transmission system 11a includes a modulation unit 31, an S / P (serial / parallel) conversion unit 32, a Fourier transform unit 33, a spectrum mapping unit 34, an inverse Fourier transform unit 35, and a P An / S (parallel / serial) conversion unit 36, a DA conversion unit 37, a local transmission unit 38, a frequency conversion unit 39, and a power amplification unit 40 are provided.

The modulation unit 31 receives communication data that is a digital signal and performs digital modulation using the communication data. For the purpose of improving PAPR (Peak to Average Power Ratio) characteristics, the modulation waveform before spectrum division may be shaped by a roll-off filter (for example, refer to the following document). Wanna) Further, encoding for error correction may or may not be performed at the time of modulation. In addition, since communication device 1 according to the present embodiment transmits communication data including the number of repetition target data, the repetition processing is performed on the modulated symbol sequence. This process will be described later. When repetition information is included in a header or the like, it is preferable that modulation is performed so that a modulated symbol sequence of the header or the like and a modulated symbol sequence of data to be repeated are different. It is. This is because the symbol sequence corresponding to the repetitive information can be demodulated before the symbol sequence synthesis (described later) at the time of reception.
Literature: Yasuo Suzuki, Hitoshi Yano, Masazumi Ueha, “Shaping effect of spectrum-divided single carrier transmission”, Society Conference of IEICE, B-5-137, p. 491, September 2010

  The S / P converter 32 converts the digitally modulated communication data into a plurality of parallel array signals. When a roll-off filter is used at the time of digital modulation, the output signal near the IFFT frame boundary is distorted, so that the S / P conversion unit 32 and the P / S conversion unit 36 perform overlapping S / P conversion and duplication. P / S conversion may be performed. The overlapping rate may be 1/8, for example.

  The Fourier transform unit 33 receives signals in a plurality of parallel arrays after S / P conversion, and converts the signals in the time domain into signals in the frequency domain by performing fast Fourier transform on these signals in parallel. The spectrum mapping unit 34 receives the signal after the fast Fourier transform, and performs spectrum mapping on the signal. Specifically, the spectrum mapping unit 34 divides the signal after the fast Fourier transform into A1 using a bandpass filter, and the frequency corresponding to a plurality of frequency bands used for communication with respect to the divided A1 signal. Perform conversion. The spectrum mapping unit 34 converts a plurality of frequency components included in a plurality of divided transmission spectrum blocks, which are signals in a parallel array after the fast Fourier transform, into a plurality of frequency bands set by the control unit 14 as described later. A mapping matrix for dividing may be generated, and a plurality of frequency components included in the plurality of divided transmission spectrum blocks may be divided into a plurality of frequency bands using the mapping matrix. For detailed processing of the spectrum mapping unit 34, see, for example, Patent Document 1 described above. When overlapping S / P conversion is performed at the time of S / P conversion, the signal phase after frequency conversion becomes discontinuous, and thus phase correction is also performed (see the above document). A1 is the number of sub-spectrums used in communication, and is an integer of 1 or more. When communication is performed using a plurality of sub-spectrums, A1 is 2 or more. The inverse Fourier transform unit 35 performs inverse fast Fourier transform on the spectrum-mapped signal and returns it to the time domain signal. The P / S conversion unit 36 receives the signal after the inverse fast Fourier transform, and converts the parallel signal into a serial signal. As described above, the P / S converter 36 may perform overlapping P / S conversion. The DA conversion unit 37 receives a serially arranged digital signal after P / S conversion, and converts the digital signal into an analog signal. The local transmitter 38 generates a signal for frequency conversion. The frequency conversion unit 39 converts the equivalent baseband transmission signal generated by the DA conversion unit 37 into a transmission frequency band using the signal for frequency conversion generated by the local transmission unit 38. The power amplification unit 40 amplifies the transmission signal frequency-converted by the frequency conversion unit 39 to a desired power. The transmission signal is transmitted via the antenna 2.

  In addition, the signal which each component of the transmission system 11a delivers may be simply called communication data. Further, the configuration of the transmission system 11a is not limited to this, and other configurations may be used as long as transmission by the spectrum division single carrier modulation method can be performed. For example, S / P conversion or P / S conversion may not be performed, or discrete Fourier transform or inverse discrete Fourier transform may be used instead of fast Fourier transform or inverse fast Fourier transform. In this way, there is arbitraryness in the configuration of the transmission system 11a. In addition, the transmission system 11a may be realized by hardware, or a part that can be realized by software may be realized by software such as a driver that drives the transmission device.

  2B, the reception system 11b includes a low noise amplification unit 41, a frequency conversion unit 42, a local transmission unit 43, an AD conversion unit 44, an S / P conversion unit 45, and a Fourier transform unit 46. A spectrum demapping unit 47, an inverse Fourier transform unit 48, a P / S conversion unit 49, and a demodulation unit 50.

  The low noise amplifying unit 41 receives an analog signal of communication data received by the antenna 2 and amplifies the received analog signal (received signal). The frequency converter 42 uses the signal generated by the local transmitter 43 to frequency-convert the received signal, and converts it to an equivalent baseband received signal that can be converted by the AD converter 44. The local transmitter 43 generates a signal for frequency conversion in the frequency converter 42. The AD converter 44 converts an analog signal that is an equivalent baseband received signal into a digital signal. The S / P converter 45 receives the digital signal after AD conversion, and converts the digital signal into a plurality of signals arranged in parallel. The Fourier transform unit 46 receives signals in a plurality of parallel arrays after S / P conversion, and converts the signals in the time domain into signals in the frequency domain by performing fast Fourier transform on these signals in parallel. The spectrum demapping unit 47 receives the signal after the fast Fourier transform and performs spectrum demapping on the signal. Specifically, the spectrum demapping unit 47 divides the signal after the fast Fourier transform into signals of A2 frequency bands corresponding to a plurality of frequency bands used in communication by a band pass filter, and the divided A2 A signal corresponding to one frequency band is combined with a signal of one frequency band by performing frequency conversion on the signal. The spectrum demapping unit 47 generates a mapping matrix corresponding to a plurality of frequency bands used in communication of communication data by the same method as the spectrum mapping unit 34, and the demapping which is a transposed matrix of the mapping matrix A matrix may be calculated, and the parallel array signals after the fast Fourier transform may be combined into one frequency band using the demapping matrix. For detailed processing of the spectrum demapping unit 47, refer to, for example, the above-mentioned Patent Document 1. A2 is the number of sub-spectrums used in communication, and is an integer of 1 or more. When communication is performed using a plurality of sub-spectrums, A2 is 2 or more. Further, when communication is performed using the spectrum division single carrier modulation method, normally, the number of sub-spectrums of communication data to be transmitted is equal to the number of sub-spectrums of communication data to be received, so A1 = A2. In some cases it may be different. The inverse Fourier transform unit 48 performs inverse fast Fourier transform on the signal after the spectrum demapping and returns it to the time domain signal. The P / S converter 49 receives the signal after the inverse fast Fourier transform, and converts the parallel signal into a serial signal. Note that, in the received communication data, when the same symbol series as that at the time of transmission is repeated, a process of combining the repeated symbol series may be performed before demodulation. This process will be described later. The demodulator 50 receives a serially arranged digital signal (symbol series) after P / S conversion, and digitally demodulates the digital signal. When symbol series are combined, demodulation is performed on the combined symbol series. If error correction encoding is performed during modulation, error correction decoding may be performed during demodulation.

  Here, also in the reception system 11b, a roll-off filter may be used in the subsequent stage of the spectrum demapping unit 47. In that case, the inverse Fourier transform unit 48 performs an inverse Fourier transform on the signal received from the roll-off filter. When a roll-off filter is used, the S / P conversion unit 45 and the P / S conversion unit 49 may perform overlap S / P conversion and overlap P / S conversion. In addition, when overlapping conversion is performed during S / P conversion, the spectrum demapping unit 47 also performs phase correction so that the signal phase does not become discontinuous.

  In addition, the signal which each component of the receiving system 11b delivers may be simply called communication data. In addition, the configuration of the reception system 11b is not limited to this, and may be another configuration as long as reception by a spectrum division single carrier modulation method can be performed. For example, S / P conversion or P / S conversion may not be performed, or discrete Fourier transform or inverse discrete Fourier transform may be used instead of fast Fourier transform or inverse fast Fourier transform. Further, in the reception system 11b, an equalization process using an equalizer (equalizer) may be performed between the Fourier transform unit 46 and the spectrum demapping unit 47. In this way, there is arbitraryness in the configuration of the reception system 11b. The reception system 11b may be realized by hardware, or a part that can be realized by software may be realized by software such as a driver that drives the reception device.

  Further, the local transmitter 38 in the transmission system 11a and the local transmitter 43 in the reception system 11b may be the same. That is, the frequency conversion in the frequency conversion units 39 and 42 may be performed using the same local transmission unit. Further, for example, the frequency generated by the local transmitters 38 and 43 is 2.4 GHz, and the frequency of the transmission signal after frequency conversion by the frequency conversion unit 39 and the frequency of the reception signal received by the antenna 2 are 2. 4 GHz, and the frequency of the transmission signal and reception signal in the equivalent baseband may be 0 GHz. Needless to say, these frequencies are merely examples and are not limited to these.

  The specifying unit 12 specifies a free frequency band that is a frequency band that is not used for communication. The vacant frequency band may be one or plural. As long as the identification unit 12 can identify the empty frequency band as a result, the method is not limited. For example, the specifying unit 12 may specify a vacant frequency band by performing carrier sense, receives a power spectrum acquired by another device (for example, AP), and uses the power spectrum to perform carrier sense and The free frequency band may be specified by performing the same thing, or the free frequency band is specified by receiving information indicating the free frequency band specified by another device (for example, AP). Also good. When the specifying unit 12 performs carrier sense, the specifying unit 12 may specify, for example, a vacant frequency band that is a frequency band having a signal strength lower than the carrier sense threshold value, or an average reception intensity. May specify a free frequency band that is a frequency band lower than the carrier sense threshold. The carrier sense may be performed during a predetermined carrier sense period. In addition, when the specifying unit 12 performs carrier sense, the specifying unit 12 may detect a free frequency band using a signal after fast Fourier transform of the reception system 11b in the communication unit 11. That is, for example, the specifying unit 12 compares the power spectrum obtained from the signal in the frequency domain after the fast Fourier transform with the carrier sense threshold. It may be determined that a large frequency band is used, and it may be determined that a frequency band having an amplitude smaller than the carrier sense threshold is not used in the carrier sense period. In addition, the specifying unit 12 may, for example, determine the overlapping frequency band between the free frequency band received from another device (for example, AP) and the free frequency band sensed by itself as the final free frequency band. It is good. In addition, the vacant frequency band may be indicated by, for example, an upper limit frequency and a lower limit frequency of the frequency band, or may be indicated by an index assigned to each frequency band in advance. In the present embodiment, the latter case will be mainly described. The index may be called a frequency index or a channel, for example. For example, the specifying unit 12 may store information indicating the specified free frequency band (for example, the frequency itself or a frequency index) in a recording medium (not shown). As a result, as long as the available frequency band can be known, the processing content performed by the specifying unit 12 is not limited. For example, the specifying unit 12 may acquire a frequency band in use. This is because even in such a case, the available frequency band can be known as a result.

  The determination unit 13 determines the number of repetitions indicating the number of data to be repeated included in the communication data according to the vacant frequency band specified by the specification unit 12. Note that data to be transmitted can be divided into data to be repeated and data that is not to be repeated. The communication data includes the number of repetition target data corresponding to the number of repetitions and one non-repetition target data. Note that there is no need for non-repetitive data. That is, all of the transmission target data may be the repetition target data. In addition, the amount of data that can be transmitted is determined according to the bandwidth (number of channels) of the vacant frequency band. Therefore, the determination unit 13 determines the number of repetitions so that the bandwidth corresponding to the data amount of the communication data is equal to or less than the bandwidth of the specified free frequency band. In addition, since the larger the available frequency band, the more data can be transmitted, the determination unit 13 determines a larger number of repetitions as the identified available frequency band is wider. Further, when the number of repetitions is the same, the larger the amount of data to be repeated, the larger the amount of data after repetition. Therefore, the determination unit 13 determines a smaller number of repetitions as the amount of data to be repeated increases. It will be. For example, the determination unit 13 may determine the maximum number of repetitions that can repeat data to be repeated in the vacant frequency band specified by the specification unit 12. This is because the higher the number of repetitions, the higher quality transmission can be performed. Note that the determination unit 13 may determine the number of repetitions equal to or less than a predetermined upper limit value. In that case, the determination unit 13 may determine the maximum number of repetitions below a predetermined upper limit value. For example, even if the vacant frequency band is very wide, not all of it is occupied, but the range below the upper limit is used. By doing so, it becomes possible to secure communication opportunities for other communication devices. Also, the more the communication is performed using a wider frequency band, the more susceptible to interference, but such a situation can be avoided by using a range below the upper limit. The predetermined upper limit value may be a predetermined value, for example, or may be a value that can change depending on the situation. In the latter case, for example, the upper limit value may be determined according to the priority of the data to be repeated, or the upper limit value may be determined according to the frequency usage status. If the priority is determined according to the priority, for example, when transmitting high priority data, the upper limit value is set high, and when transmitting low priority data, the upper limit value is set low. May be. That is, an upper limit value that becomes higher as the priority is higher may be set. In addition, when the frequency is determined according to the use situation of the frequency, for example, when the vacant frequency band is very wide, a large upper limit is set, and when the vacant frequency band is not very wide, a small upper limit is set. It may be set. That is, an upper limit value that becomes higher as the vacant frequency band is wider may be set. Further, the usable frequency band (number of channels) may be determined according to the processing by the communication unit 11. For example, the number of channels that can be used for communication may be discrete, such as 1, 2, 4, 5, 8, 9, etc., depending on the number of points in the fast Fourier transform. In that case, the determination unit 13 determines that the bandwidth corresponding to the data amount of the communication data is equal to or less than the bandwidth of the frequency band that can be used by the communication unit 11 among the specified vacant frequency bands. Determine the number of repetitions. For example, in the case of the above example, even if the number of empty channels specified by the specifying unit 12 is 7, the determining unit 13 responds to 5 channels that can be used by the communication unit 11 among the 7 channels. The number of repetitions may be determined.

  The control unit 14 causes the communication unit 11 to transmit communication data including the number of repetitions determined by the determination unit 13 in the symbol series after modulation of the data to be repeated. If the number of repetitions determined by the determination unit 13 is N (N is an integer of 1 or 2 or more), the control unit 14 causes the communication unit 11 to transmit communication data including N symbol sequences after modulation. Therefore, for example, the control unit 14 receives a modulated symbol sequence from the modulation unit 31, generates a symbol sequence by repeating the symbol sequence N times, and passes the generated symbol sequence to the S / P conversion unit 32. Alternatively, the symbol sequence modulated by the modulation unit 31 may be controlled to be read N times by the S / P conversion unit 32, and the S / P conversion may be performed on the N symbol sequences. As described above, if the communication unit 11 is controlled such that communication data including N symbol sequences modulated by the modulation unit 31 is transmitted, the control method is not limited.

  In addition, when communication data including a plurality of symbol sequences corresponding to data to be repeated is received, the control unit 14 receives the plurality of symbol sequences from the P / S conversion unit 49 and synthesizes the symbol sequences. . Then, the combined symbol series is passed to the demodulation unit 50. The synthesis of the symbol series is performed by adding the symbols included in the symbol series. For example, if the number of repetitions in the communication data received by the communication unit 11 is N times (N is an integer of 1 or 2 or more), the control unit 14 combines N symbol sequences to obtain one symbol sequence. The symbol sequence may be generated and passed to the demodulator 50. Note that the control unit 14 may use the repetition information received from the transmission source device in order to identify the repeated portion in the symbol sequence after P / S conversion. When the repetition information is included in the header or the like, the control unit 14 first demodulates the symbol sequence corresponding to the data that is not the repetition target (for example, the header or the like), and acquires the repetition information from the demodulation result. Then, N symbol sequences may be combined using the repetition information.

  In addition, the control unit 14 causes the communication unit 11 to communicate communication data using the vacant frequency band specified by the specifying unit 12. Specifically, the control unit 14 selects one or a plurality of vacant frequency bands from the vacant frequency bands specified by the specifying unit 12, and causes communication data to communicate in the selected vacant frequency bands. The communication may be reception or transmission. When the communication is reception, for example, the control unit 14 may cause the communication unit 11 to transmit information indicating the selected free frequency band to the communication destination device. As a result, communication data using the selected frequency bands is transmitted from the communication destination device, and the communication unit 11 receives the communication data. The transmission by the communication unit 11 may be performed using a control channel, for example. In addition, when the communication performed using the free frequency band selected by the control unit 14 is transmission, the control unit 14 causes the communication unit 11 to transmit communication data using the selected free frequency band, for example. Also good. As a result, transmission using the selected frequency band is performed. It is assumed that the selected frequency band is a frequency band in which communication data including data to be repeated for the number of repetitions determined by the determination unit 13 can be transmitted. The selection of the frequency band to be used by the control unit 14 is well known in DSA and will not be described in detail.

  Here, the determination of the number of repetitions will be briefly described. In order to simplify the description, a case where the frequency band is designated by the number of channels will be described. Usually, the symbol rate in one-channel communication is fixed. Therefore, if a modulation method (for example, QPSK, 16QAM, etc.) used for digital modulation and a coding rate (for example, 1/2, 3/4, etc.) are determined, communication is performed by one communication using M channels. The number of possible data bytes will be determined. Here, it is assumed that the number of free channels is “A”. In addition, the number of bytes of data that can be communicated in one communication using M channels is “B (M)”, and the number of bytes of data to be repeated that is to be transmitted in one communication is “C”. The number of bytes of data that is not the object of repetition (for example, a header) is “D”. Then, the determination unit 13 first determines the number of usable channels “E”. As described above, the number of usable channels “E (≦ A)” is determined according to the limit in the communication unit 11, the upper limit value, and the like. If there is no limit such as the upper limit value of the number of channels, E = A. When the number of usable channels “E” is determined, the maximum number of bytes “B (E)” that can be transmitted is determined. Therefore, the repetition number “F” is F = floor ((B (E) −D) / C). Here, floor (x) is a floor function of a real number x, and is a maximum integer less than or equal to x. Therefore, the determination unit 13 can determine the number of repetitions in this way. In addition, the number of channels “G” used in transmission of communication data including data corresponding to the number of repetitions is a minimum integer value satisfying B (G) ≧ C × F + D. The number of channels “G” may be calculated by the control unit 14. Then, the control unit 14 selects the G channels from the empty channels, and the communication unit 11 performs communication using the selected G channels. In the above description, the processing is performed in units of bytes, but it is needless to say that the above processing may be performed in units of bits because final adjustment by bit padding is possible.

  Next, the operation of the communication apparatus 1 will be described using the flowchart of FIG. Note that the flowchart in FIG. 3 shows processing related to communication in the data channel, and does not include communication in the control channel. The repetition information is transmitted via the control channel.

  (Step S101) The communication unit 11 determines whether to perform transmission. If transmission is to be performed, the process proceeds to step S102. If not, the process proceeds to step S108. Note that, for example, the communication unit 11 may determine that transmission is performed when there is data to be transmitted, or may determine that transmission is performed at another timing.

  (Step S102) The specifying unit 12 specifies an empty frequency band.

  (Step S103) The determination unit 13 determines the number of repetitions according to the data amount to be repeated, the free frequency band, and the like.

  (Step S104) The modulation unit 31 modulates data to be transmitted. As a result, a symbol series corresponding to the transmission target data is obtained.

  (Step S105) The control unit 14 determines whether the number of repetitions is 2 or more. If the number of repetitions is 2 or more, the process proceeds to step S106. If the number of repetitions is 1, the process proceeds to step S107.

  (Step S106) The control unit 14 performs control so that the modulated symbol series of the data to be repeated is repeated by the number of repetitions determined by the determination unit 13.

  (Step S <b> 107) The control unit 14 causes the communication unit 11 to transmit communication data including the number of repetitions determined by the determination unit 13 to the symbol sequence after modulation of the data to be repeated. Then, the process returns to step S101.

  (Step S108) The communication unit 11 determines whether communication data has been received. If the communication data is received, the process proceeds to step S109. If not, the process returns to step S101.

  (Step S109) The control unit 14 determines whether or not repetition target data is repeated in the received communication data. If the process is repeated, the process proceeds to step S110. If not, the process proceeds to step S111. For example, the control unit 14 determines that the repetition is performed when the repetition information is received via the control channel, and determines that the repetition is not performed when the repetition information is not received. May be.

  (Step S110) The control unit 14 combines the number of symbol sequences corresponding to the number of repetitions.

(Step S111) The demodulator 50 demodulates the combined symbol series or the unsynthesized symbol series. Then, the process returns to step S101.
In the flowchart of FIG. 3, as described above, transmission / reception of repetitive information is not clearly described. For example, the communication unit 11 transmits the repetitive information to the communication partner prior to or together with the transmission in step S107. You may transmit to the apparatus of. Further, prior to the reception of step S108 or simultaneously with the reception, the communication unit 11 may repeatedly receive information from the communication partner device. In the flowchart of FIG. 3, the process ends when the power is turned off or the process is terminated.

  Here, an example of communication data will be described. FIG. 4A is a diagram illustrating communication data having a repetition number “1”. The portion to be repeated indicated by “Repetition 1” includes “data” that is data to be transmitted, a CRC (Cyclic Redundancy Check) bit “CRC” used for error detection, and a terminal position. Included trellis bits “T” and padding “MPAD” added for modulation. At the time of modulation, the repetition target is digitally modulated and converted into a symbol series. Note that padding indicated by SPAD is added to the end of the communication data. FIG. 4B is a diagram illustrating communication data having a repetition number “2”, and FIG. 4C is a diagram illustrating communication data having a repetition number “3”. As shown in FIGS. 4B and 4C, the amount of data increases as the number of repetitions increases, and a wider communication band is required. Even when the number of repetitions is “4” or more, the communication data includes the portion to be repeated as many times as the number of repetitions, as in FIGS. 4B and 4C. Note that the larger the number of repetitions, the wider the bandwidth is transmitted. That is, the larger the number of repetitions, the more data is transmitted in the frequency direction and transmitted. Therefore, it can be considered that the diffusion rate is indicated by the number of repetitions. When the communication data includes data that does not repeat, for example, as shown in FIG. 4D, data that is not a repetition target may be included between the preamble and “repetition 1”. The non-repeating data may have the same structure as the repetition 1 shown in FIG. 4A, or may not. Usually, the data to be repeated is data used other than communication, such as data used in a destination application or the like, and the data not to be repeated is data used in communication, for example. Therefore, for example, the packet payload may be data to be repeated, and the packet header may be data not to be repeated. Note that this is an example, and data used in communication such as a header may be a target of repetition. That is, at least a part of the transmission target data may be repeated data.

  Next, the operation of the communication device 1 according to the present embodiment will be described using a specific example. First, the frequency channel configuration of the DSA system operating in the 2.4 GHz ISM band in this specific example will be briefly described. The system bandwidth is 80 MHz, and 80 frequency channels with a bandwidth of 1 MHz are provided. The 16 channels whose frequency channel numbers end with 1 or 6 are designated as control channels and used for transmission of control information such as channel allocation information. Other channels are designated as data channels and are used for payload transmission. The control channel is changed in units of time frames based on the hopping pattern. This is to ensure a transmission opportunity even when a part of the band is occupied by another system. Also, inter-cell interference is avoided by limiting the data channel selection range according to the control channel to be used. The time frame of the DSA system is composed of a transmission stop period of 200 μs in length used for spectrum sensing of each frequency channel, and 8 slots (each slot is 600 μs) used for information transmission that follows. Four slots are allocated to each of the downlink and the uplink. In addition, the same number and the same number of slots are assigned to the MS that performs data transmission in both downlink and uplink. Both the AP and the MS perform sensing in the transmission stop period, and transmit the control channel packet via the control channel only when it is determined that the band scheduled to be used as the control channel is unused. The control channel packet includes a result of sensing in the frequency channel performed on the sender side, information corresponding to a physical header of the data channel packet such as data channel selection information, transmission payload length, modulation setting to be used, and a part of MAC Header information is stored. An appropriate number of usable data channels are selected simultaneously with the transmission of the control channel packet, and if necessary, the data channel packet for payload transmission is transmitted while performing spectrum division. The AP determines whether or not each frequency channel can be used based only on its own sensing result. On the other hand, the MS determines that only the frequency channel determined as unused in both the AP-side sensing result notified from the AP and the result of the sensing performed by the MS can be used. Therefore, the MS does not transmit its own packet when the downlink control channel packet is not normally received. In addition, information is repeatedly transmitted and received through the control channel.

  Further, in this specific example, it is assumed that the correspondence among the modulation scheme, coding rate, MCSID, and number of transmittable bytes is as shown in FIG. In FIG. 5, MCSID is information for identifying MCS (Modulation and Coding Scheme). The number of bytes that can be transmitted in FIG. 5A is the number of bytes that can be transmitted in one channel when using 4 slots, and the number of bytes that can be transmitted in FIG. 5B is 8 channels when using 4 slots. The number of transmittable bytes in FIG. 5C is the number of transmittable bytes for 9 channels when 4 slots are used. For example, in the case of the modulation method “QPSK” and the coding rate “1/2”, the number of bytes that can be transmitted in 8 channels is “1440 (bytes)”. Note that the modulation scheme and coding rate may be determined according to the amount of data to be transmitted. For example, when the amount of data to be transmitted is large, a modulation method and coding rate that can transmit more data, that is, a modulation method corresponding to a large MCSID value is selected, and the amount of data to be transmitted is small. In this case, a modulation scheme and a coding rate that can perform more stable transmission, that is, a modulation scheme corresponding to a small value of MCSID may be selected.

  In this specific example, the number of usable channels is assumed to be 1, 2, 4, 5, 8, 9, 16, 20,. In this specific example, it is assumed that “QPSK” is adopted as the modulation scheme and “1/2” is adopted as the coding rate. In this specific example, it is assumed that communication using four slots is performed.

  First, it is assumed that data to be transmitted is transferred to the communication unit 11, and the communication unit 11 determines that it is time to perform transmission (step S101). In this case, it is assumed that all the data to be transmitted that is desired to be transmitted in one communication is the data to be repeated, and the capacity (size) is 460 bytes. The communication unit 11 passes the data capacity to the determination unit 13 and the control unit 14. Next, the specifying unit 12 performs carrier sense and specifies an empty frequency band (step S102). Here, it is assumed that 10 data channels are identified as free. Then, the specifying unit 12 passes information indicating the 10 free channels to the control unit 14 and passes the number of free channels “10” to the determining unit 13.

  Of the number of free channels “10”, the maximum number that the communication unit 11 can use is “9”. Therefore, the determination unit 13 sets the number of transmittable bytes “1621” when 9 channels are used, Using the number of bytes of data “460”, floor (1621/460) = 3 is calculated, and the number of repetitions is determined to be “3” (step S103). The repetition number “3” is passed to the control unit 14. When receiving the repetition number, the control unit 14 calculates 460 × 3 = 1380, and specifies the minimum number of channels “8” that can transmit the number of bytes. Also, the modulation unit 31 of the communication unit 11 modulates data to be repeated, and passes the modulated symbol sequence to the control unit 14 (step S104). Since the number of repetitions received from the determination unit 13 is “3” (step S105), the control unit 14 performs S / P conversion on the symbol sequence corresponding to FIG. 4C in which the modulated symbol sequence is repeated three times. It passes to the part 32 (step S106). And the control part 14 controls the communication part 11 so that communication using eight channels selected from ten empty channels may be performed (step S107). Note that the repetition information including the eight channels selected by the control unit 14, the capacity of the data to be repeated 460 (bytes), and the repetition number “3” is separately transmitted via the control channel. It is assumed that it is transmitted to the device. In this way, communication data repeatedly including data to be transmitted (data to be repeated) is transmitted.

  Next, a case where communication data repeatedly including data to be repeated is received will be described. In this case, it is assumed that the data channel through which the communication data is transmitted and the repetitive information are transmitted to the communication apparatus 1 in advance via the control channel. Then, it is assumed that the repetition information indicates that the number of repetitions is 3 and the capacity of the data to be repeated is 440 (bytes). When the communication unit 11 receives communication data in such a situation (step S108), the control unit 14 determines that the repetition is performed (step S109), and is repeated in the symbol sequence after the P / S conversion. 3 symbol sequences are identified. Then, a combination of the three symbol sequences is passed to the demodulator 50 (step S110). The demodulator 50 demodulates the symbol sequence that is the result of the synthesis (step S111). Thereafter, the demodulated communication data is appropriately used in the communication device 1 and other devices.

  As described above, according to the communication device 1 according to the present embodiment, when there are many free frequency bands, it is possible to transmit communication data in which repetition of data to be repeated is increased. As a result, by combining the repeated target data on the receiving side, the bit error rate can be reduced, and high-quality communication can be realized. In particular, in communication using an empty frequency band, short-term and regular communication opportunities are not secured, so reliable retransmission cannot be guaranteed, but such transmission is necessary by performing such transmission. Can prevent the situation from happening. For example, when transmitting data that requires real-time properties such as video data and audio data, it is not preferable that a short-term / periodic communication opportunity is not ensured. As in the communication device 1 according to the above, by transmitting communication data including repeated data, retransmission can be reduced, and real-time performance can be more easily ensured in communication using an empty frequency band. In addition, since the transmission is performed within the available frequency band, it is considered that there is almost no influence on other communications. Further, in communication in the ISM band or the like, when the own device performs communication in a certain frequency band, the other device performs communication using a frequency band different from the frequency band. Therefore, when communication data includes a signal corresponding to a plurality of data to be repeated, compared to a case where the signal is not so, a wider bandwidth will be secured and more stable communication can be continued. Conceivable.

In the present embodiment, a case has been described in which communication device 1 receives repeated communication data of data to be repeated, but this need not be the case. The communication device 1 only transmits repeated communication data of data to be repeated, and does not need to receive such communication data. In this case, the control unit 14 does not have to perform control processing for combining repeated symbol sequences in the received communication data.
Further, the communication according to the present embodiment may be performed in the ISM band, for example, or may be performed in a band other than that.

  In the above embodiment, each process or each function may be realized by centralized processing by a single device or a single system, or may be distributedly processed by a plurality of devices or a plurality of systems. It may be realized by doing.

  In the above embodiment, the information exchange between the components is performed by one component when, for example, the two components that exchange the information are physically different from each other. It may be performed by outputting information and receiving information by the other component, or when two components that exchange information are physically the same, one component May be performed by moving from the phase of the process corresponding to to the phase of the process corresponding to the other component.

  In the above embodiment, information related to processing executed by each component, for example, information received, acquired, selected, generated, transmitted, or received by each component In addition, information such as threshold values, mathematical formulas, addresses, etc. used by each component in processing is retained temporarily or over a long period of time on a recording medium (not shown) even when not explicitly stated in the above description. It may be. Further, the storage of information in the recording medium (not shown) may be performed by each component or a storage unit (not shown). Further, reading of information from the recording medium (not shown) may be performed by each component or a reading unit (not shown).

  In the above embodiment, when information used by each component, for example, information such as a threshold value, an address, and various setting values used by each component may be changed by the user Even if it is not specified in the above description, the user may be able to change the information as appropriate, or it may not be. If the information can be changed by the user, the change is realized by, for example, a not-shown receiving unit that receives a change instruction from the user and a changing unit (not shown) that changes the information in accordance with the change instruction. May be. The change instruction received by the receiving unit (not shown) may be received from an input device, information received via a communication line, or information read from a predetermined recording medium, for example. .

  In the above embodiment, when two or more components included in the communication apparatus 1 include a communication device or an input device, the two or more components may physically include a single device. Alternatively, it may have a separate device.

  In the above embodiment, each component may be configured by dedicated hardware, or a component that can be realized by software may be realized by executing a program. For example, each component can be realized by a program execution unit such as a CPU reading and executing a software program recorded on a recording medium such as a hard disk or a semiconductor memory. At the time of execution, the program execution unit may execute the program while accessing the storage unit or the recording medium. The software that realizes the communication device in the above embodiment is the following program. That is, this program is a program for causing a computer to function as the communication device 1 that performs communication using an empty frequency band, and a specifying unit that specifies an empty frequency band that is a frequency band that is not used for communication, A determining unit that determines the number of repetitions indicating the number of data to be repeated included in the communication data according to the vacant frequency band specified by the specifying unit, and a repetition in which the determining unit determines a symbol sequence after modulation of the data to be repeated This is a program for causing a communication unit including a number to function as a control unit that transmits the communication data using the vacant frequency band specified by the specifying unit.

  In the program, the functions realized by the program do not include functions that can be realized only by hardware. For example, a function that can be realized only by hardware such as a modem or an interface card in a component that acquires information, a component that outputs information, or the like is not included at least in the function realized by the program.

  Further, this program may be executed by being downloaded from a server or the like, and a program recorded on a predetermined recording medium (for example, an optical disk such as a CD-ROM, a magnetic disk, a semiconductor memory, or the like) is read out. May be executed by Further, this program may be used as a program constituting a program product.

  Further, the computer that executes this program may be singular or plural. That is, centralized processing may be performed, or distributed processing may be performed.

  FIG. 6 is a schematic diagram illustrating an example of an external appearance of a computer that executes the program and realizes the communication device 1 according to the embodiment. The above-described embodiment can be realized by computer hardware and a computer program executed on the computer hardware.

  In FIG. 6, a computer system 900 includes a computer 901 including a CD-ROM (Compact Disk Read Only Memory) drive 905, an FD (Floppy (registered trademark) Disk) drive 906, a keyboard 902, a mouse 903, a monitor 904, and the like. Is provided.

  FIG. 7 is a diagram showing an internal configuration of the computer system 900. In FIG. 7, in addition to the CD-ROM drive 905 and the FD drive 906, a computer 901 is connected to an MPU (Micro Processing Unit) 911, a ROM 912 for storing a program such as a bootup program, and the MPU 911. A RAM (Random Access Memory) 913 that temporarily stores program instructions and provides a temporary storage space, a hard disk 914 that stores application programs, system programs, and data, and an MPU 911 and a ROM 912 are interconnected. And a bus 915. Note that the computer 901 may include hardware for performing the above-described transmission and reception processing, for example, a DA converter, an AD converter, a modulator, a demodulator, or the like. It may be connected. The computer 901 may include a network card (not shown) that provides connection to a LAN, WAN, or the like.

  A program that causes the computer system 900 to execute the function of the communication device 1 according to the above-described embodiment is stored in the CD-ROM 921 or FD 922, inserted into the CD-ROM drive 905 or FD drive 906, and transferred to the hard disk 914. May be. Instead, the program may be transmitted to the computer 901 via a network (not shown) and stored in the hard disk 914. The program is loaded into the RAM 913 when executed. The program may be loaded directly from the CD-ROM 921, the FD 922, or the network.

  The program does not necessarily include an operating system (OS), a third party program, or the like that causes the computer 901 to execute the functions of the communication device 1 according to the above-described embodiment. The program may include only a part of an instruction that calls an appropriate function (module) in a controlled manner and obtains a desired result. How the computer system 900 operates is well known and will not be described in detail.

  Further, the present invention is not limited to the above-described embodiment, and various modifications are possible, and it goes without saying that these are also included in the scope of the present invention.

  As described above, according to the communication device or the like according to the present invention, an effect that the bit error rate can be reduced is obtained, and it is useful as a communication device or the like that performs communication using an empty frequency band.

DESCRIPTION OF SYMBOLS 1 Communication apparatus 2 Antenna 11 Communication part 11a Transmission system 11b Reception system 12 Identification part 13 Determination part 14 Control part 31 Modulation part 32, 45 S / P conversion part 33, 46 Fourier transform part 34 Spectrum mapping part 35, 48 Inverse Fourier transform Unit 36, 49 P / S conversion unit 37 DA conversion unit 38, 43 Local transmission unit 39, 42 Frequency conversion unit 40 Power amplification unit 41 Low noise amplification unit 44 AD conversion unit 47 Spectrum demapping unit 50 Demodulation unit

Claims (6)

A communication device that performs communication using an empty frequency band,
A communication unit for communicating communication data;
A specifying unit for specifying an empty frequency band that is a frequency band that is not used for communication;
A determination unit that determines the number of repetitions indicating the number of repetition target data included in the communication data according to the bandwidth of the vacant frequency band identified by the identification unit;
A control unit that causes the communication unit to transmit communication data including the number of repetitions determined by the determination unit, including the symbol sequence after modulation of the data to be repeated, using the empty frequency band specified by the specification unit. Communication equipment. The communication device according to claim 1, wherein the determining unit determines the number of repetitions as a maximum number of data that can be repeated in the empty frequency band specified by the specifying unit. The communication device according to claim 1, wherein the determination unit determines the number of repetitions as a number equal to or less than a predetermined upper limit value. The communication apparatus according to claim 1, wherein the communication unit also transmits repetitive information that is information that can identify a repeated symbol sequence included in the communication data. A communication method for performing communication using an empty frequency band,
A specific step of identifying a free frequency band that is a frequency band that is not used for communication;
A determination step of determining a repetition number indicating the number of data to be repeated included in the communication data according to the bandwidth of the free frequency band specified in the specifying step;
And a control step of transmitting communication data including the number of repetitions determined in the determination step by using the vacant frequency band specified in the specifying step. Computer
A program for functioning as a communication device that performs communication using an empty frequency band,
A specifying unit for specifying a free frequency band that is a frequency band not used for communication;
A determination unit that determines the number of repetitions indicating the number of repetition target data to be included in communication data according to the bandwidth of the free frequency band specified by the identification unit, and
A program for functioning as a control unit that transmits communication data including a symbol sequence after modulation of data to be repeated by the number of repetitions determined by the determination unit using an empty frequency band specified by the specification unit.

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